VIDEO : Katherine Schwarzenegger Celebrates 26th Birthday With Family

The daughter of Arnold Schwarzenegger and Maria Shriver turned 26 on Sunday and celebrated her birthday over the weekend with her family. Katherine's brother Patrick Schwarzenegger, 22, posted on his Instagram page an adorable photo of himself with Katherine, their parents and siblings Christina Schwarzenegger, 24, and Christopher Schwarzenegger, 18, standing around a birthday cake. Katherine shared on her Instagram page a photo of herself at a joint birthday party with friends. Happy 26th birthday Katherine," her mother said on her Instagram page, alongside a throwback head shot of Katherine. "You are beautiful inside & out I love you to the moon and back @katherineschwarzengger." Arnold also shared a heartwarming birthday tribute pic.